Core-shell Al@Al2O3, which was obtained by hydrothermal surface oxidation of Al metal particles, was used as the support in supported Ni catalysts for CO and CO2 methanation. The core-shell micro-structured support (Al@Al2O3) helped develop a highly efficient Ni-based catalyst compared with conventional gamma-Al2O3 for these reactions. Moreover, the deposition-precipitation method was shown to outperform the wet impregnation method in the preparation of the active supported Ni catalysts. The catalysts were characterized using various techniques, namely, N-2 physisorption, H-2 chemisorption, CO2 chemisorption, temperature-programmed reduction with H-2, temperature-programmed desorption after CO2 adsorption, X-ray diffraction, inductively coupled plasma-atomic emission spectroscopy, high-resolution transmission electron microscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy. Higher Ni dispersion when using Al@Al2O3 as the support and the deposition-precipitation method resulted in better catalytic performance for CO methanation. Furthermore, the higher density of medium basic sites and enhanced CO2 adsorption capacity observed for Ni/Al@Al2O3 helped increase catalytic activity for CO2 methanation.